In a number of industries it is very common to use valves to regulate the mixing of different ingredients or to regulate the flow in pipe systems by activating certain valves and thereby opening or closing the flow of the different mediums. For an example in a dairy plant it is common that the plant is equipped with a number of such valves and actuators. The valves are for instance used during cleaning of the pipes in the plant, during mixing and during filling of processed products into cartons.
When projecting the plant it is considered according to the different processes and according to relevant regulative whether to use a normally closed or a normally open valve. The difference of the two types of normal position is all in the actuator. After having projected the plant the actuators and/or valves are ordered from the supplier with the specified configuration. It is, however, possible to change an actuator from normally closed to normally open or vice versa. Such an operation is not easy and a number of parts in the actuator have to be either replaced or rearranged in another position. Thus, it is a time consuming job and further it is a job that demands skilled personnel as such actuators often is with preloaded mechanical springs, which are not easy to take apart and rebuild. Some types of actuators require not only a rebuild, but simply have to be changed into another actuator with the desired normal position.